Information about tissue structure is used for so-called cancer screenings, in particular in mammography. US 2009/0022273 A1 describes an X-ray system for mammography exposures. Further, it is known to acquire X-ray images in order to be able to make an assessment of volumetric breast density, which breast density is a key feature or a key characteristic, for detection and prediction of cancer such as breast cancer. However, it has been shown that the assessment of volumetric breast density from conventional mammograms may result in false predictions due to the influence of a 3D breast model estimation on the accuracy of the calculation.